Operating System (OS) Firewall

"In computing, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted network and an untrusted network, such as the Internet." Wikipedia

To illustrate, Windows 10 comes with its own embedded software firewall by default enabled, however over time this may have been disabled for some reason.

Value-added hint: You can ensure firewall is enabled

Step 1: Clicking the Windows icon on the bottom left of your screen, type the Word "Firewall" > click on this to check the Firewall types are enabled.

Step 2: Check status. Green (as seen above) indicates that your firewall is on. Should you wish to change the status (off or on) you will usually find a place to do so nearby. For example, on this screen you would navigate to the left-hand sidebar and select 'Turn Windows Defender Firewall on or off'.

Note that should your machine be part of a corporate domain or you have managed IT services by an IT company, these settings may be controlled by your IT Administrator and you will be unable to change it yourself.

Note: This slide is based on Microsoft and Windows 10 information